PROCESS OF PRODUCING LIGHT OLEFINS AND AROMATICS FROM WIDE RANGE BOILING POINT NAPHTHA

Abstract

Systems and methods for processing full range naphtha to produce light olefins are disclosed. The systems and methods include separating the full range naphtha into a light naphtha stream and a heavy naphtha stream and integrating a catalytic cracking with a naphtha reforming to process the light naphtha and heavy naphtha streams.

Claims

1. A method for processing full range naphtha, the method comprising: feeding full range naphtha to a separation unit, the full range naphtha having a final boiling point less than 250° C.; separating the naphtha, in the separation unit, to produce a light naphtha stream having a final boiling point in a range of 60° C. to 110° C. and a heavy naphtha stream having a final boiling point less than 250° C.; hydrotreating the heavy naphtha stream in a hydrotreatment unit to produce a hydrotreated stream; separating the hydrotreated stream to produce a paraffinic stream comprising primarily paraffins and a reformable stream; reforming the reformable stream to produce an aromatic stream comprising greater than 50 wt. % aromatics; combining the light naphtha stream with the paraffinic stream to produce a combined stream; catalytically cracking the combined stream to form a cracked stream; separating the cracked stream to produce a plurality of product streams that include a first stream that comprises primarily C.sub.2 to C.sub.3 paraffins; and steam cracking the first stream to produce C.sub.2 to C.sub.4 olefins.

2. The method of claim 1, further comprising recovering C.sub.2 to C.sub.4 olefins.

3. The method of claim 1, wherein the steam cracking is performed under process conditions including a cracking temperature of 600 to 1000° C. and a residence time of 0.1 to 100 s.

4. The method of claim 1, wherein the separation unit comprises a distillation unit.

5. The method of claim 1, wherein the separation unit is operated under process conditions including an operating temperature of 73 K (−200° C.) to 373 K (100° C.).

6. The method of claim 1, wherein the separation unit is operated under process conditions including an operating pressure of 0.5 to 50 bar.

7. The method of claim 1, wherein the catalytic cracking is performed under process conditions including an operating temperature of 600 to 750° C.

8. The method of claim 1, wherein the catalytic cracking is performed under process conditions including an operating pressure of 1 to 4 bar.

9. The method of claim 1, wherein the catalytic cracking is performed in the presence of a catalyst selected from the group consisting of an active amorphous clay-type catalyst, a crystalline molecular sieve, X-type zeolites, Y-type zeolites, ferrierite, erionite, mordenite, faujasite, ST-5, ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38, ZSM-48, germanium, gallium, and combinations thereof.

10. The method of claim 1, wherein separating the hydrotreated stream comprises distilling.

11. The method of claim 1, wherein the full range naphtha is obtained from distilling crude oil.

12. The method of claim 1 further comprising the step of separating the hydrotreated stream to produce a C.sub.6 to C.sub.12 paraffinic stream and a reformable stream comprising naphthene and aromatic components from the heavy naphtha stream; and reforming the reformable stream to produce an aromatic stream comprising at least 50 wt. % aromatics.

13. The method according to claim 12, wherein the separating of the cracked stream produces a plurality of product streams that include (1) a first stream that comprises primarily C.sub.2 to C.sub.3 paraffins, (2) a second stream comprising primarily methane (CH.sub.4) and hydrogen (H.sub.2), (3) a third stream comprising primarily C.sub.2 to C.sub.4 olefins, (4) a fourth stream primarily comprising C.sub.4 to C.sub.6 hydrocarbons, (5) a fifth stream comprising primarily fuel oil, and (6) a sixth stream comprising C.sub.6-C.sub.12 hydrocarbons; and steam cracking the first stream to produce C.sub.2 to C.sub.4 olefins.

14. The method of claim 1, wherein the full range naphtha comprises 20 to 60 wt. % paraffins, 5 to 35 wt. % naphthenes, and 5 to 35 wt. % aromatics.

15. The method of claim 1, wherein the light naphtha comprises primarily C.sub.5 to C.sub.6 hydrocarbons.

16. The method of claim 1, wherein 35 wt. % to 90 wt. % olefins and aromatics are produced per mass unit of naphtha.

17. The method of claim 1, wherein the hydrotreating removes at least one member selected from the group consisting of sulfur and nitrogen.

18. The method of claim 1, wherein unconverted hydrocarbons from the catalytic cracking are returned for further catalytic cracking.

19. The method of claim 1, wherein the conditions for the hydrotreating include a temperature in a range of 300° C. to 500° C., a pressure in a range of about 50 psig to about 2000 psig, and a space velocity of 0.1 LHSV to 20.0 LHSV.

20. A system for producing light olefins from a full range naphtha feed, the system comprising: a separation unit for separating a full range naphtha feed into a light naphtha stream and a heavy naphtha stream; a hydrotreater for hydrotreating the heavy naphtha stream; a separator for separating the hydrotreated heavy naphtha stream into a C.sub.6 to C.sub.12 paraffins containing stream and a reformable stream; a reforming unit for reforming the reformable stream to produce aromatics; a light naphtha catalytic cracking unit for cracking light naphtha and paraffins into a catalytically cracked product; a separator for separating the catalytically cracked product to yield a light olefin stream, a C.sub.2 to C.sub.3 paraffin stream and a C.sub.7 to C.sub.12 hydrocarbon stream; and a steam cracker for steam cracking the C.sub.2 to C.sub.3 paraffin stream to produce light olefins.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0039] For a more complete understanding, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

[0040] FIG. 1 shows a system for producing light olefins from full range naphtha according to the invention integrating naphtha reforming and cracking processes.

[0041] FIG. 2 shows a schematic diagram for a method for producing light olefins from full range naphtha, according to embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0042] A discovery has been made of a process and a system that addresses the current problems associated with processing full range naphtha to yield light olefins and other products. The process includes the use of an integrated naphtha reforming process and a cracking process for catalytically cracking light naphtha. The light naphtha is separated from the full range naphtha and fed to a catalytic cracker such as an (fluid catalytic cracker) FCC, while the heavy naphtha is hydrotreated, paraffins removed via separation, and the product is fed to a reforming unit. The removed paraffins are optionally combined with the light naphtha stream and cracked. The cracked product is separated into various streams, including a light olefin stream which are then either recovered or further processed. A C.sub.2 to C.sub.3 paraffin stream produced by separating the cracked light naphtha stream may be further processed to yield additional light olefins.

[0043] FIG. 1 shows a system 100 for producing light olefins from full range naphtha by integrating naphtha reforming and cracking processes, according to embodiments of the invention. The full range naphtha feed stream 10 may be supplied to system 100 from other refinery processes such as a crude oil distillation process. The full range naphtha feed stream 10 includes a heavy naphtha component and a light naphtha component. Full range naphtha feed stream 10 is supplied via a separation unit inlet to a full range naphtha separation unit 101 which can separate the full range naphtha feed into a stream containing primarily light naphtha 11 and heavy naphtha 12. Light naphtha stream 11 exits an outlet of the full range naphtha separation unit 101 and is fed to cracking unit 105 via an inlet, preferably after mixing with a C.sub.6 to C.sub.12 paraffinic stream 13 containing primarily paraffins as described further below. Light naphtha cracking unit 105 is preferably a fluid catalytic cracker that cracks light naphtha, paraffins, or other hydrocarbons to yield a first cracked product effluent stream 15 containing light olefins that exits the light naphtha cracking unit 105 via an outlet.

[0044] The conditions in cracker 105 may include a temperature of from 400 to 1000° C., preferably from 450 to 900° C., and more preferably from 500 to 800° C.

[0045] Flow rates through the cracker may include diluted steam and possibly dry gas to control the partial pressure of hydrocarbons and improve catalyst fluidization.

[0046] If the cracker is a fluid catalytic cracker, the catalyst includes, preferably, catalysts that are used in the art of fluidized catalytic cracking, such as active amorphous clay-type catalyst or crystalline molecular sieves. Zeolites are commonly used molecular sieves in FCC processes. Others that may be used include X-type zeolites, Y-type zeolites, ferrierite, erionite, mordenite, faujasite, ST-5, ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38 and ZSM-48, germanium, gallium, or any combination thereof.

[0047] First cracked product effluent stream 15 is fed via an inlet into a second separation unit 106 that separates a light olefin stream 23 containing the desired light olefins that exits separation unit 106 via an outlet, and other products from the first cracked product effluent stream 15. Those other products may include a methane and hydrogen containing stream 24, which exits the second separation unit 106 via an outlet, a first stream 19 that contains primarily C.sub.2 to C.sub.3 paraffins that exits second separation unit 106 via an outlet, C.sub.7 to C.sub.12 hydrocarbon stream 20 that exits second separation unit 106 via an outlet, C.sub.4 to C.sub.6 hydrocarbon stream 17 that exits second separation unit 106 via an outlet, and a fuel oil stream 22 that exits second separation unit 106 via an outlet. Any of the streams exiting second separation unit 106 may be recovered or further processed, as described further below.

[0048] Second separation unit 106 may include a series of separation vessels, distillation columns, gas compressors, quench towers, caustic tower, dryers and other equipment known in the art.

[0049] The C.sub.2 to C.sub.3 paraffin containing first stream 19 is optionally and preferably fed to steam cracker 107 via an inlet and steam cracked to produce light olefins 21, which is recovered and combined with the light olefin, 23 from second separation unit 106.

[0050] The conditions in the steam cracker may include dilution steam and processed in conventional steam cracking furnaces. The steam cracking furnaces operating conditions are known in the industry and by people of skill in the art.

[0051] Heavy naphtha stream 12 exits first separation unit 101 via an outlet and is fed into a hydrotreatment unit 102 via an inlet to produce hydrotreated stream 14. Preferably, C.sub.7 to C.sub.12 containing hydrocarbon stream 20 from second separation unit 106 is also fed into hydrotreatment unit 102 via an inlet, and the streams 12 and 20 are hydrotreated to yield hydrotreated stream 14, which exits hydrotreatment unit 102 via an outlet and is fed to third separation unit 103 via an inlet. Third separation unit 103 separates hydrotreated stream 14 into a paraffinic stream 13 which exits via an outlet and a reformable stream 16 which exits third separation unit 103 via an outlet. Paraffinic stream 13 preferably contains primarily C.sub.6 to C.sub.12 hydrocarbons. Reformable stream 16 is then routed to a reforming unit 104 via an inlet, while paraffinic stream 13 is mixed with light naphtha containing stream 11 to form mixed stream 30, which is fed into cracking unit 105 via an inlet where it is cracked as described above. Not shown in the figure, the steam 12 is combined with hydrogen to carry out the hydrotreatment chemistry.

[0052] The C.sub.4 to C.sub.6 hydrocarbon stream 17 is routed to cracker 105 via an inlet where it is cracked along with the hydrocarbons of combined stream 30. Stream 30 is formed by combining light naphtha stream 11 and paraffinic stream 13 prior to entering light naphtha cracker 105.

[0053] Reforming unit 104 reforms the hydrocarbons of reformable stream 16 to produce, among other things, aromatics which exit reforming unit 104 via an outlet as aromatic stream 18. The aromatics include BTX may be recovered.

[0054] FIG. 2 is a process scheme diagram of cracking process integrated with the naphtha reforming associated with the required separation unit. The full range naphtha feed is split into light naphtha and heavy naphtha. The heavy naphtha is combined with a stream from the catalytic cracking unit recovery section having C.sub.6 to C.sub.12 hydrocarbons where both streams are hydrogenated/hydrotreated to remove impurities and saturate the olefins. The paraffins in the hydrotreated stream are further extracted leaving an easily reformable stream. The light naphtha and extracted paraffins are combined to make the feed for catalytic cracking.

[0055] According to embodiments of the invention, method 200 includes catalytic cracking of light naphtha and paraffins and reforming of heavy naphtha. The process begins at block 201 with the separation of light and heavy naphtha streams from a full range naphtha feed. The light naphtha feed processing is shown on the left, while heavy naphtha stream processing is shown on the right. At block 204, the light naphtha stream is catalytically cracked to produce light olefins and other products. In embodiments of the invention, catalytic cracking at block 204 is performed in catalytic cracking unit 105. Catalytic cracking unit 105 may comprise one or more catalytic cracking reactors and preferably is a fluid catalytic cracker. In embodiments of the invention, the catalytic cracking reactor may include a fixed bed reactor, a moving bed reactor, or a fluidized bed reactor. Catalytic cracking reactor 105 may include a catalyst comprising crystalline aluminosilicate (zeolites) clay-type filler and binder. The catalyst may also contain active matrix. Zeolites are commonly used molecular sieves (also known as crystalline aluminosilicate) in FCC processes. Others that may be used include X-type zeolites, Y-type zeolites, ferrierite, erionite, mordenite, faujasite, ST-5, ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38 and ZSM-48, germanium, gallium, or combinations thereof.

[0056] In embodiments of the invention, the reaction conditions for catalytic cracking at block 204 may include a reaction temperature of 600 to 800° C. and all ranges and values there between, including 600 to 610° C., 610 to 620° C., 620 to 630° C., 630 to 640° C., 640 to 650° C., 650 to 660° C., 660 to 670° C., 670 to 680° C., 680 to 690° C., and 690 to 700° C., and 700 to 800° C., and most preferably 800° C. The reaction conditions for catalytic cracking at block 204 may further include a reaction pressure of 0.5 to 10 bar and all ranges and values there between. The reaction conditions may further include a weight hourly space velocity in a range of 0.1 to 1000 hr.sup.−1 and all ranges and values there between.

[0057] The products from the catalytic cracking unit are separated at block 206 into fuel oil light olefins, C.sub.2 to C.sub.3 paraffins, a C.sub.4 to C.sub.6 stream, a C.sub.7 to C.sub.12 stream and a CH.sub.4/H.sub.2 stream. The C.sub.2 to C.sub.3 paraffins are further converted in a steam cracking furnace 214 to light olefins. The C.sub.4 to C.sub.6 is recycled back to the catalytic cracker at block 204.

[0058] The C.sub.2 to C.sub.3 paraffin containing stream is steam cracked in a steam cracker unit to produce additional light olefins. The conditions in the steam cracker unit may include high temperature up to 1000° C. and low residence time of less than 100 seconds.

[0059] Turning now to treatment of the heavy stream, at block 203 heavy naphtha is hydrotreated to remove sulfur, nitrogen, if present, and undesirable di-olefin and olefin components. The hydrotreated effluent is separated at step 205 into a paraffin stream and olefins, if present, that is preferably combined with the light naphtha in block 202, and the remainder is reformed in a heavy naphtha reforming unit at step 207 to yield aromatics which are recovered at step 209. The conditions in the hydrotreater unit include a temperature less than 550° C., pressure in the range of 2 to 50 bars. In addition, hydrogen should be combined in certain ratio with the hydrotreater feed. The hydrotreated product contains less sulfur and/or nitrogen than the initial product, and aromatics are formed.

[0060] The conditions in the reforming unit include a temperature range from 450° C. to 580° C., and a pressure range from 1 to 50 bars.

[0061] Although embodiments of the present application and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the embodiments as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, and composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the above disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.